Technical Field
The present disclosure generally relates to an electrophotographic image forming apparatus such as a copier, a facsimile machine, a printer, or a multifunction peripheral (MFP, i.e., a multifunction machine) having at least two of copying, printing, facsimile transmission, plotting, and scanning capabilities and, more particularly, to an image forming apparatus including a developing device employing two-component developer.
Description of the Related Art
Developing devices employing two-component developer including toner and carrier (hereinafter “two-component developing devices”) are widely used in image forming apparatuses such as photocopiers, facsimile machines, printers, and MFPs.
In such two-component developing devices, the developer is carried on a developing roller (i.e., a developer bearer) after fully stirred in the developing device. After a developer regulator (e.g., a doctor blade) disposed facing the developing roller adjusts the amount of the developer carried on the developing roller, the developer reaches a position (i.e., a development gap) facing a photoconductor drum (i.e., an image bearer) as the developing roller rotates. In the development gap, an electrical field (developing potential) is generated between the developing roller, to which a developing bias is applied, and the photoconductor drum having a latent image potential. Then, the toner in the two-component developer adheres to a latent image on the photoconductor drum due to the electrical field.
In such image forming apparatuses, to reliably produce images having a desirable image density, so-called process control is executed, for example, after power-on or recovery from a standby mode, before the start of standard image formation. The process control is to adjust image forming conditions, such as, the developing potential (a difference between the developing bias and the latent image potential) and toner concentration (i.e., the ratio of toner in the developer contained in the developing device).
For example, a toner patch is formed on an intermediate transfer belt, the image density of the toner patch is detected, and the developing potential, the toner concentration, or both are adjusted based on the detection results.